Gas detector



FIG. 1 is an underneath front plan view of a gas detector showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front end view thereof;

FIG. 4 is a rear end view thereof;

FIG. 5 is a left side view thereof; and,

FIG. 6 is a right side view thereof. 

The ornamental design for a gas detector, as shown and described. 